Questions tagged [focus]

Focus is the mechanism of converging light from a point light source onto an imaging plane by a lens.

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12
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3answers
2k views

Do convex lenses make parallel light rays of different wavelength converge to different points?

I'm starting to study cameras and lenses. By reading explanations and watching videos on convex lenses, I learnt that they make parallel light rays converge to a single point called the focal point. ...
36
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9answers
31k views

How to nail focus for DSLR astrophotography?

I've been doing a bit of astrophotography and the problem that I almost always have is nailing focus. I'll manually focus on a bright star or the moon (which hopefully isn't an option!) by magnifying ...
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1answer
95 views

Are internal focusing primes actually uncompensated varifocal lenses?

If I shorten the focal length of a lens without taking any other measures, that will reduce the required flange distance for infinity focus - meaning that if the actual flange distance is not changed, ...
0
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2answers
484 views

Why can't I turn the focus ring on my Vivitar 100-300mm far enough to get infinity focus?

I recently bought VIVITAR 100-300mm F5.6-6.7 macro zoom. I use it with Nikon D70S. Here is my problem. When distance between my D70S with VIVITAR and object of photography is 15meters and more, I can ...
0
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3answers
152 views

Does the autofocus system look through the lenses?

I have a doubt about the effect of putting a filter (polarizer, UV etc) on the autofocus system. In theory, a lens which is put in front of the lens will affect the focus (we must set a different ...
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2answers
289 views

Why doesn't lens focus after turning focusing ring while set to autofocus?

My brother tried my new camera and was turning the focusing ring quite harshly on auto focus. (50mm canon lens) I’ve read multiple similar questions but nothing is quite what I mean. Ever since my ...
5
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2answers
887 views

If I swap cameras, will my lens keep appropriate focus?

I'll be going to a place where the night sky is quite nice to photograph. I plan on taking a star trail long exposure shot with a Canon 3000N, an analog camera. I'm pretty sure it won't be able to ...
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0answers
31 views

Which Lens will keep the subject and background in focus? [duplicate]

I am an amateur photographer. I have a normal lens 28-80 lens. When I take a picture with this lens the subject in the photo comes into focus but the background remains blurred. I have another lens ...
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4answers
2k views

After I dropped my lens, focus locks but images are blurry — what could be wrong?

I have a Tamron 24-70 2.8 on a D610. I usually go for small apertures (F11 to 16) since I work with flashes on studio setups, my lens gives sharp images on those appertures but anything below F5.6 ...
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0answers
27 views

Fuji X-T2 focusing point in interval shooting and video

This might be a dumb question but why can't I see or pick the focusing point when in interval shooting and video? When shooting video it does autofocus if I quickly move between shooting something ...
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3answers
214 views

Reason for offset in lens/sensor and tripod mount?

I have noticed that my Canon Powershot G11 tripod mount is more in the center of the body of the camera and not aligned with the lens/sensor. Is there a reason for this? My concern is that as I rotate ...
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1answer
140 views

Why is there a maximum focus distance when using an extension tube? [duplicate]

I am using the Nikon D850 together with the Sigma 50mm/1.4 Art and the MEIKE MK-N-AF1-A extension tube(s). During first shots I found out that the combination not only has a minimum focus distance (...
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2answers
316 views

Are electronically parfocal RF lenses parfocal enough for fireworks photography with zoom?

Within a month or so, it's the first time I'll see fireworks as an owner of a good camera and naturally I'm planning to take photographs of them. By researching various fireworks photography sources, ...
4
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5answers
244 views

Is it best to use a wide aperture when I'm focusing at infinity and depth of field is not a concern?

If I shoot at f1.4, I can easily separate my subject from background due to the shallow DoF. In the case where I turn the focus to infinity at f1.4, I will have everything in focus, except the ...
19
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7answers
10k views

Can software auto-detect image focus?

I was wondering if there was any photo management software out there that could auto detect and "rate" images on how in focus they are. This comes up for me quite commonly when i am looking through a ...
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6answers
210 views

Can we prove that the object is not tilted from photo(s)?

This is an image of Al-Masjid an-Nabawi. Can we from this image, or from combination of images available online say with a certain degree of confidence (prove?) that this red circled minaret is ...
3
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0answers
78 views

AF Fine-tune zoom lenses?

How do you fix / fine-tune the focus on a zoom lens? Nikon states The D850 can fine-tune autofocus automatically. The results can be used with all lenses of the same type. But does it also mean ...
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3answers
132 views

Focus in Analog and Digital Cameras [duplicate]

Why a subject not in focus in the viewfinder of an analog camera is seen as two misaligned half circles, while in that of a digital camera is evenly blurred?
16
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5answers
4k views

Why can't my custom camera body focus to far distances?

I have built a custom optical device that uses a standard C-mount lens as found on CCTV cameras. Wikipedia states that the flange-to-film distance of a C-mount lens is 17.526 millimetres. I have ...
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3answers
144 views

What affects tripod stability?

I have a Vanguard Veo 2 265 CB tripod. I really like it and it has been performing, but lately I am trying to get my pictures as sharp as I can get and I noticed something. It must be trivial to ask,...
3
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2answers
130 views

Does shift based perspective correction have any effect on focus?

Consider a photographer with an SLR camera and a PC lens attached in its default, unshifted position, standing on the ground at the base of a columned building whose height is X times that of the ...
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4answers
100 views

Would it be viable to use my camera as a low power microscope?

I sometimes do pcb soldering and it is useful to have a microscope on hand with zoom of anywhere between 7x-12x to view the tiny components. I don't really want to spend several hundred dollars on a ...
2
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1answer
79 views

Back-focusing with Canon 7D2 body and Sigma 50mm art lens: is the Sigma USB dock the solution?

I just bought a second hand Sigma lens (50mm Art f/1.4) for my Canon 7D2 body (Mark II). This combination yields a very serious back-focus problem: With no micro-ajustements correction on my body, ...
0
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2answers
163 views

Nikon D5200 no longer focuses

It used to be that on my Nikon D5200 camera holding down the shoot button halfway the viewfinder would show green dots and it would focus nicely. Now after resetting the camera settings, replacing ...
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2answers
92 views

How to focus old manual viewfinder cameras?

I recently got two really old cameras, and I'm lost. The cameras are an Agfa Silette, and a Welta Weltax. I expected the cameras to have a focusing mechanism similar to rangefinger cameras, or split-...
12
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4answers
122k views

How can I fix an out-of-focus blurred photo in Photoshop?

How can I fix this picture? Somebody else took this picture and well he wasn't able to do it very well, and it's blurred. I have photoshop
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3answers
6k views

Why does this lens lose focus when you zoom in but not when you zoom out?

This is regarding the Sony 18-105 E-mount constant-aperture zoom. I took at photo at 18mm, focusing manually: I then zoomed to 105mm, and took another photo, keeping the same focus: Notice that the ...
16
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6answers
8k views

Why aren't faces sharp in my f/1.8 portraits even though I'm carefully using center-point autofocus?

I love my Canon Rebel T6 and take portrait pictures in Av mode with a 50mm in 1.8 Av. I'm using auto focus in the 'focus on center point' mode. I make sure that the center point focuses on the face so ...
0
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2answers
92 views

Focus issues even when using Single-Point [duplicate]

I have been noticing, even if I use AF-S with Single-Point focus and set the focus on the eye of the bird, still the final photo either comes out blurred or has less details. Someone in a response to ...
0
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2answers
146 views

How do I find infinity focus with a kit lens when there's not enough light for optical verification? [duplicate]

I have a D7200 which I want to use at long distances in low light photography. The kit lens, a 18-140 does not have focus markers on it. Furthermore, the focus ring does not stop hard at any point. ...
0
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2answers
142 views

How to set focus when subject is more than one object?

I have taken a photo with men dancing in a group. It was rejected by an agency stating: "The main subject is not in focus and grain noticed in the photo". Below I am giving the cropped image. Since ...
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2answers
111 views

How can a subject stay in focus if the shot is recomposed afterwards?

I have a doubt about a procedure that I see many photographers continuously apply and they taught me. I see that, when they want to take a picture with their reflex, they do this sequence of steps: 1)...
1
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3answers
142 views

How to identify main subject of the photo and set focus?

I am using Nikon D5600. While on street photo shoot, I clicked a couple of photos and submitted on one of the stock photo website. Few photos got approved whereas few were rejected with a comment. ...
0
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1answer
88 views

How can I tell whether or not a lens has focus breathing?

So recently I got a 90mm macro lens, installed a focus bracketing app onto my camera and let it run. Unfortunately, turned out that this lens has focus breathing which means the actual zoom level in ...
0
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2answers
188 views

What makes these white stars appear black?

This is partial screenshot from an episode of the TV (Netflix) show Daredevil (season 2, episode 7): Note how the normally white stars of the US flag are showing up as black - albeit quite out of ...
4
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2answers
141 views

How can I focus on someone who is in motion and still get them in focus with a wide aperture?

I'm trying to figure out the best technique to use for photographing people in motion. I would love to do weddings one day - but for now I’m concentrating on just getting my focus down (with a very ...
1
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4answers
413 views

How do fixed lenses “focus” on things at different distances? [duplicate]

I'm trying to understand depth of field and I'm struggling. If I'm playing with a 50mm fixed lens, and I alter its focus using the little ring around the lens, what is actually changing in terms of ...
0
votes
1answer
252 views

Focusing issues on live view - Nikon D750 w/ AF-S NIKKOR 24-70mm f/2.8G ED

On a heavily used Nikon D750 w/ AF-S NIKKOR 24-70mm f/2.8G ED: When using live vision, ussualy while holding the camera up over my head, autofocus focuses nowhere. This happens right after having ...
39
votes
8answers
22k views

How can I get sharp manual focus despite poor eyesight?

I suffer from astigmatism. It's only mild, though I feel it's affecting what I'm seeing when looking through the viewfinder. Frequently, after shooting a photo with my Canon EOS 7D, I'll load it into ...
0
votes
2answers
253 views

Why do I get so many unsharp pictures with my Canon 70-200 IS f/2.8?

Please take a look at the picture below. You can see where the focus point was thanks to a LR plugin. But the image is unsharp - again. And yes, I'm sure the dog was standing still enough for 1/250 ...
0
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2answers
99 views

Is minimum focus distance (MFD) really minimum?

On my prime lense the barrel shows the "minimum" focus distance (MFD). According to the definition you find on internet you cannot focus an object closer to this distance (measure from the sensor ...
0
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1answer
25 views

Canon EOS80D would not focus [duplicate]

While in manual mode with auto focus, could not get the camera to focus for night astrophotography. Tried different combinations of ISO, TV and AV. I noticed that the EV was all the way to the right....
2
votes
2answers
112 views

When using Back Button Auto Focus, do I release the button before shooting a sequence, or hold it down?

When shooting moving subjects (Sports), am I suppose to keep the back button AF pressed during a sequence of shots? Or do I press til it focuses, and then let go and shoot a sequence? Thank you in ...
2
votes
4answers
148 views

Can hyperfocal distance be used to keep everyone in focus in group photography?

If you have different sets of people standing at different linear distances from the camera can we use the theory of hyperfocal distance to ensure sharp focus on all subjects? Conversely does being "...
3
votes
1answer
99 views

What is the Job of second lens in dual camera Mobile phones

Somewhere I read that two lenses are required to create a DSLR effect- Blurring the background. But today I read, the Aperture size is responsible for blurring the background, So any lens (single ...
0
votes
2answers
112 views

DSLR lens image inversion?

 Out of simple curiosity, do DSLR cameras produce an inverted image on the sensor, with the image being flipped by software?  I've dabbled with astronomy prior to my current interest in ...
1
vote
3answers
124 views

Is there any mirrorless camera that can mark areas within DoF in the EVF?

All mirrorless cameras have the image in the rear LCD and the electronic viewfinder (EVF) fully generated by a computer, making many utilities such as noise removal, text overlays, histograms, etc ...
1
vote
3answers
240 views

Does image quality of the lens affect “focus and recompose” technique?

As I understand it, 'focus and recompose' is often used to ensure the subject is in focus and at the same time composition is right. It has been estimated that some lenses are best in terms of image ...
0
votes
2answers
375 views

Is the Canon EF 24-105mm f/4L IS USM lens parfocal or not?

I read a review of the Canon EF 24-105mm f/4L IS USM lens. It said: Focus shifts while zooming. Zoom before you focus. Surprised by this (I don't recall ever seeing the focus scale shift while ...
2
votes
2answers
173 views

Would adding an external lens allow one area outside the focal plane to be in focus?

I’m doing high speed scientific imaging. I have a camera mounted in a fixed location with a Micro Nikkor 105mm lens. It’s viewing a fixed subject that has a small mirror oriented 45 degrees underneath ...